The present invention relates generally to devices for spacing overhead parallel conductors, and particularly to a rigid bar device adapted to be clamped to and between the conductors by resilient metal clips in a simple and economical manner.
Since the beginning of the use of spacers for spacing the subconductors of overhead conductor bundles, the spacers have generally employed clamps having threaded bolts to attach each spacer to the subconductors. The use of bolts has presented the problem of determining whether or not the bolts are in fact tight and the clamps thus properly secured to the conductors. For the person inspecting the spacer and clamps, the bolt and clamps might appear tightly installed but in reality, they might be quite loose such that the clamp on the conductor wears the conductor before the spacing device eventually falls from the line.
On the other hand, the lineman installing the spacer might overtighten the bolt, which can leave the bolt in a partially fractured condition. As soon as certain loads are placed on the spacer, such as might occur with strong winds and/or substantial motions of the conductor, the bolt breaks leaving the clamp loose (again) on the conductor. A partial solution to the problem of overtightening has been the use of a bolt with a breakaway head. When the bolt is tightened to a designated torque, the head shears off thus furnishing the personnel installing the sapcer with an obvious indication of correct installation torque. Also, it provides ease of inspection from the ground, as the inspector would have only to visually determine that the breakaway head was in fact missing.
The breakaway head did not, however, wholly solve the problem of quick and accurate determination of whether or not a spacer clamp was properly secured and bolted to its associated conductor. Occasionally, the tapped hole in the casting of the clamp was under tolerance or simply had faulty threads. The bolt also might be in similar condition, and the threads of the bolt or the casting might have foreign matter on them. The installer, under these conditions, tightens the bolt, shears off the breakaway head, with the bolt having little, if any, tension in securing the clamp to the conductor. The result, again, is a loose clamp and, eventually, a damaged conductor.
In addition to the above problems, an inadequate clamp design can result in properly installed bolts working loose. The conductor to which the bolt is attached, being subject to changing temperatures, expands and contracts. If the total area of the clamp bearing on the conductor is inadequate, the conductor material is compressed to a degree that the bolts of the clamps are allowed to work loose since such compression can result in the loss of considerable tension on the bolts of the clamps.
Further, there have even been instances when installers have failed to break off any of the breakaway heads of clamp bolts on entire sections of a transmission line, and inspectors have failed to observe such a condition.
Because of these problems with bolted clamps, purchasers of such clamps, such as power and transmission line companies, have opted for conductor clamping devices that do not use threaded bolts.
A device for spacing overhead conductors that does not require threaded bolts is shown in the U.S. Gill et al Pat. No. 2,915,580. This device comprises two cast bars having opposed pins and pin receiving holes in the bars, as well as dove-tail slots for receiving dove-tail keys to secure the bars together. It will be noted that to install such a device, an application of forces directed at 90.degree. to each other is required to compress the bars on the conductors and to insert the dove-tail keys into the slots in the bars. Under severe conditions, and operating from a cart suspended from the conductors high above the ground, the application of such perpendicular forces might not be easily accomplished in the process of installing the Gill spacer.
In addition, the keys of the Gill structure might appear, from the ground, to be fully inserted and secure within the bar slots but in fact they may not be fully inserted and secure. For this reason, the degree of assurance of proper attachment is similar to that of the bolted structures discussed above.
Another device for spacing overhead conductors that does not require the use of threaded bolts is shown in U.S. Torr Pat. No. 3,161,721. The Torr device utilizes a pin extending through two half portions of a conductor clamp, the pin having at one of its ends a head for engaging one clamping half and a transverse cotter extending through the pin to overlie the other clamping half when the clamping halves are disposed in clamping position. While avoiding certain of the above-discussed problems associated with threaded bolts, the structure of Torr requires certain manufacturing steps and costs and is susceptible to only partial securance of the clamp to the conductor so that a thoroughly doubt-free clamping mechanism is still needed in the conductor spacing art.